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Wave Cut Platform

Wave cut platform

A wave cut platform refers to the narrow flat area often seen at the base of a sea cliff caused by the action of the waves. Where the coast line itself is changing due to seismic action there may be a series of platforms showing earlier sea levels and giving an indication of the amount of uplift caused by various earthquakes. Because of the continual wave action a wave cut platform represents an extremely hostile environment and few but the toughest of organisms can utilize such a niche. The phenomenon is also known as a marine terrace. See also: Landform, Beach, Raised beach. Category:Landforms

Wave

:This article is about waves in the most general scientific sense; a separate article focuses on ocean waves. For other meanings see wave (disambiguation). Soundwave redirects here. for the Transformers character, see Soundwave (Transformers) A wave is a disturbance that propagates in a periodically repeating fashion, often transferring energy. A mechanical wave exists in a medium (which on deformation is capable of producing elastic restoring forces) through which they travel and can transfer energy from one place to another without any of the particles of the medium being displaced permanently; there is no associated mass transport. Instead, any particular point oscillates around a fixed position. However, electromagnetic radiation, and probably gravitational radiation are not mechanical waves, and can travel through a vacuum, without a medium. Waves are characterised by crests (highs) and troughs (lows), either perpendicular (in the case of transverse waves) or parallel (in the case of longitudinal waves) to wave motion.
The medium which carries a wave
A medium that can carry a wave is classified by one or more of the following properties:
- A linear medium if the amplitudes of different waves at any particular point in the medium can be added.
- A bounded medium if it is finite in extent, otherwise unbounded.
- A uniform medium if its physical properties are unchanged at different locations in space.
- An isotropic medium if its physical properties are the same in different directions.
Examples of waves
troughs
- Ocean surface waves, which are perturbations that propagate through water (see also surfing and tsunami).
- Visible light, radio waves, x-rays, gamma rays, infrared rays, and ultraviolet rays make up electromagnetic radiation. In this case propagation is possible without a medium, through vacuum. These electromagnetic waves travel at about 300,000 km/s.
- Sound - a mechanical wave that propagates through air, liquid or solids, and is of a frequency detected by the auditory system. Similar are seismic waves in earthquakes, of which there are the S, P and L kinds.
- Gravitational waves, which are fluctuations in the gravitational field predicted by General relativity. These waves are nonlinear.
Characteristic properties
All waves have common behaviour under a number of standard situations. All waves can experience the following:
- Reflection – the change of direction of waves, due to hitting a reflective surface.
- Refraction – the change of direction of a wave due to them entering a new medium.
- Diffraction – the spreading out of waves, for example when they travel through a small slit.
- Interference – the superposition of two waves that come into contact with each other.
- Dispersion – the splitting up of waves by frequency.
- Rectilinear propagation – the movement of waves in straight lines.
Transverse and longitudinal waves
Rectilinear propagation Transverse waves are those with vibrations perpendicular to the direction of the propagation of the wave; examples include waves on a string and electromagnetic waves. Longitudinal waves are those with vibrations parallel to the direction of the propagation of the wave; examples include most sound waves. Ripples on the surface of a pond are actually a combination of transverse and longitudinal waves; therefore, the points on the surface follow elliptical paths.
Polarization
Transverse waves can be polarized. Unpolarised waves can oscillate in any direction in the plane perpendicular to the direction of travel, while polarized waves oscillate in only one direction perpendicular to the line of travel.
Physical description of a wave
Image:wave.png Waves can be described using a number of standard variables including: frequency, wavelength, amplitude and period. The amplitude of a wave is the measure of the magnitude of the maximum disturbance in the medium during one wave cycle, and is measured in units depending on the type of wave. For examples, waves on a string have an amplitude expressed as a distance (meters), sound waves as pressure (pascals) and electromagnetic waves as the amplitude of the electric field (volts/meter). The amplitude may be constant (in which case the wave is a c.w. or continuous wave) or may vary with time and/or position. The form of the variation of amplitude is called the envelope of the wave. The period (T) is the time for one complete cycle for an oscillation of a wave. The frequency (F) is how many periods per unit time (for example one second) and is measured in hertz. These are related by: : $f=\frac$ When waves are expressed mathematically, the angular frequency (ω, radians/second) is often used; it is related to the frequency f by: : $f=\frac$ .
Travelling waves
Waves that remain in one place are called standing waves - e.g. vibrations on a violin string. Waves that are moving are called travelling waves, and have a disturbance that varies both with time t and distance z. This can be expressed mathematically as: : $y=A(z,t) \cos (\omega t - kz + \phi),\,f$ where A(z, t) is the amplitude envelope of the wave, k is the wave number and φ is the phase. The velocity v of this wave is given by: : $v=\frac= \lambda f,$ where λ is the wavelength of the wave.
Propagation through strings
The speed of a wave travelling along a string (v) is directly proportional to the square root of the tension (T) over the linear density (ρ): : $v=\sqrt.$ This equation can be found using dimensional analysis
The wave equation
The wave equation is a differential equation which describes a harmonic wave passing through a medium, discussed above. The equation has different forms depending on how the wave is transmitted, and on what medium. Not all waves are sinusoidal. One example of a non-sinusoidal wave is a pulse that travels down a rope resting on the ground, extending in direction x, travelling at velocity c. The height of the pulse above the ground is φ. The distance the pulse travels between some time t and time 0 is ct. In one dimension the wave equation has the form : $\frac\frac=\frac. \$ A general solution, given by d'Alembert is : $\phi(x,t)=F(x-ct)+G(x+ct). \$ considered to be the shapes of two pulses travelling down the rope, F in the +x direction, and G in the -x direction. If we substitute for x above, instead directions x, y, z, we then can describe a wave propagating in three dimensions. A non-linear wave-equation can cause mass transport. The Schrödinger equation describes the wave-like behaviour of particles in quantum mechanics. Solutions of this equation are wave functions which can be used to describe the probability density of a particle. Quantum mechanics also describes particle properties that other waves, such as light and sound, have on the atomic scale and below.
External links

- [http://www.lightandmatter.com/area1book3.html Vibrations and Waves] - an online textbook
- [http://kestrel.nmt.edu/~raymond/classes/ph13xbook/node1.html A Radically Modern Approach to Introductory Physics] - an online physics textbook that starts with waves rather than mechanics
See also

- List of wave topics
- Capillary waves
- Doppler effect
- Group velocity
- Phase velocity
- Ripple tank
- Standing wave
- Audience wave
- Ocean surface wave
- Waving Category:Partial differential equations ko:파동 ms:Gelombang ja:波動 simple:Wave

Earthquake

: An earthquake is a sudden and sometimes catastrophic movement of a part of the Earth's surface. Earthquakes result from the dynamic release of elastic strain energy that radiates seismic waves. Earthquakes typically result from the movement of faults, planar zones of deformation within the Earth's upper crust. The word earthquake is also widely used to indicate the source region itself. The Earth's lithosphere is a patch work of plates in slow but constant motion (see plate tectonics). Earthquakes occur where the stress resulting from the differential motion of these plates exceeds the strength of the crust. The highest stress (and possible weakest zones) are most often found at the boundaries of the tectonic plates and hence these locations are where the majority of earthquakes occur. Events located at plate boundaries are called interplate earthquakes; the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes (see New Madrid Seismic Zone). Earthquakes also occur in volcanic regions and as the result of a number of anthropogenic sources, such as reservoir induced seismicity, mining and the removal or injection of fluids into the crust. Seismic waves including some strong enough to be felt by humans can also be caused by explosions (chemical or nuclear), landslides, and collapse of old mine shafts, though these sources are not strictly earthquakes.

Characteristics

Large numbers of earthquakes occur on a daily basis on Earth, but the majority of them are detected only by seismometers and cause no damage ([http://neic.usgs.gov/neis/general/magnitude_intensity.html magnitude] 5). Most earthquakes occur in narrow regions around plate boundaries down to depths of a few tens of kilometres where the crust is rigid enough to support the elastic strain. Where the crust is thicker and colder they will occur at greater depths and the opposite in areas that are hot. At subduction zones where plates descend into the mantle earthquakes have been recorded to a depth of 600 km. Large earthquakes can cause serious destruction and massive loss of life through a variety of agents of damage, including fault rupture, vibratory ground motion (i.e., shaking), inundation (e.g., tsunami, seiche, dam failure), various kinds of permanent ground failure (e.g. liquefaction, landslide), and fire or a release of hazardous materials. In a particular earthquake, any of these agents of damage can dominate, and historically each has caused major damage and great loss of life, but for most of the earthquakes shaking is the dominant and most widespread cause of damage. There are four types of seismic waves that are all generated simultaneously and can be felt on the ground. S-waves (secondary or shear waves) and the two types of surfaces waves (Love waves and Rayleigh waves) are responsible for the shaking hazard. Rayleigh waves Rayleigh waves Most large earthquakes are accompanied by other, smaller ones, that can occur either before or after the principal quake — these are known as foreshocks or aftershocks, respectively. While almost all earthquakes have aftershocks, foreshocks are far less common occurring in only about 10% of events. The power of an earthquake is distributed over a significant area, but in the case of large earthquakes, it can spread over the entire planet. Ground motions caused by very distant earthquakes are called teleseisms. The Rayleigh waves from the Sumatra-Andaman Earthquake of 2004 caused ground motion of over 1 cm even at the seismometers that were located the greatest distance from it. Using such ground motion records from around the world it is possible to identify a point from which the earthquake's seismic waves appear to originate. That point is called its "focus" or "hypocenter" and usually proves to be the point at which the fault slip was initiated. The location on the surface directly above the hypocenter is known as the "epicenter". The total size of the fault that slips, the rupture zone, can be as large as 1000 km, for the biggest earthquakes. Just as a large loudspeaker can produce a greater volume of sound than a smaller one, large faults are capable of higher magnitude earthquakes than smaller faults are. Earthquakes, especially those that occur beneath oceans or seas (also called seaquake) and have large vertical displacements, can give rise to tsunamis, either as a direct result of the deformation of the sea bed due to the earthquake, or as a result of submarine landslips or "slides" indirectly triggered by it.

Earthquake Size

The first method of quantifying earthquakes was intensity scales. In the United States the Mercalli (or Modified Mercalli, MM) scale, is commonly used while Japan (shindo) and the EU (European Macroseismic Scale) each have their own scales. These assign a numeric value (different for each scale) to a location based on the size of the shaking experienced there. The values 6 (normally denoted ‘’VI’’) in the MM scale for example is: Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage. The problem with these scales is the measurement is subjective, often based on the worst damage in an area and influenced by local effects like site conditions that make it a poor measure for the relative size of different events in different places. For some tasks related to engineering and local planning it is still useful for the very same reasons and thus still collected. If you feel an earthquake in the US you can report the effects to the USGS here: [http://pasadena.wr.usgs.gov/shake/ Did you feel it?] The first attempt to qualitatively define one value to describe the size of earthquakes was the magnitude scale (the name being taking from similar formed scales used on the brightness of stars). In the 1930s, a California seismologist named Charles F. Richter devised a simple numerical scale (which he called the magnitude) to describe the relative sizes of earthquakes in Southern California. This is known as the “Richter scale”, “Richter Magnitude” or “Local Magnitude” (M_L). It is obtained by measuring the maximum amplitude of a recording on a Wood-Anderson torsion seismometer (or one calibrated to it) at a distance of 600km from the earthquake. Other more recent Magnitude measurements include: body wave magnitude (m_b), surface wave magnitude (M_s) and duration magnitude (M_D). Each of these is scaled to gives values similar to the values given by the Richter scale. However as each is also based on the measurement of one part of the seismogram they do not measure the overall power of the source and can suffer from saturation at higher magnitude values (larger events fail to produce higher magnitude values).These scales are also empirical and as such there is no physical meaning to the values. They are still useful however as they can be rapidly calculated, there are catalogues of them dating back many years and are they are familiar to the public. Seismologists now favor a measure called the seismic moment, related to the concept of moment in physics, to measure the size of a seismic source. The seismic moment is calculated from seismograms but can also by obtained from geologic estimates of the size of the fault rupture and the displacement. The values of moments for different earthquakes ranges over several order of magnitude. As a result the moment magnitude (M_W) scale was introduced by Hiroo Kanamori, which is comparable to the other magnitude scales but will not saturate at higher values. seismogram on February 28 2001.]] 2001 of the shaking of the Nisqually earthquake on February 28 2001.]]

Causes

Most earthquakes are powered by the release of the elastic strain that accumulate over time, typically, at the boundaries of the plates that make up the Earth's lithosphere via a process called Elastic-rebound theory. The Earth is made up of tectonic plates driven by the heat in the Earth's core. these plates collide against each other all the time but sometimes the gaps between them are stressed. Eventually, the plates make way and all that energy is sent out in the form of seismic waves. Deep focus earthquakes, at depths of 100's km, are possibly generated as subducted lithospheric material catastrophically undergoes a phase transition since at the pressures and temperatures present at such depth elastic strain cannot be supported. Some earthquakes are also caused by the movement of magma in volcanoes, and such quakes can be an early warning of volcanic eruptions. A rare few earthquakes have been associated with the build-up of large masses of water behind dams, such as the Kariba Dam in Zambia, Africa, and with the injection or extraction of fluids into the Earth's crust (e.g. at certain geothermal power plants and at the Rocky Mountain Arsenal). Such earthquakes occur because the strength of the Earth's crust can be modified by fluid pressure. Earthquakes have also been known to be caused by the removal of natural gas from subsurface deposits, for instance in the northern Netherlands. Finally, ground shaking can also result from the detonation of explosives. Thus scientists have been able to monitor, using the tools of seismology, nuclear weapons tests performed by governments that were not disclosing information about these tests along normal channels. Earthquakes such as these, that are caused by human activity, are referred to by the term induced seismicity. Another type of movement of the Earth is observed by terrestrial spectroscopy. These oscillations of the earth are either due to the deformation of the Earth by tide caused by the Moon or the Sun, or other phenomena.

Preparation for earthquakes

- Emergency preparedness
- Household seismic safety
- Seismic retrofit
- Earthquake prediction

Specific fault articles

- Alpine Fault
- Calaveras Fault
- Hayward Fault Zone
- North Anatolian Fault Zone
- New Madrid Fault Zone
- San Andreas Fault

Specific earthquake articles

- Shaanxi Earthquake (1556). Deadliest known earthquake in history, estimated to have killed 830,000 in China.
- Cascadia Earthquake (1700).
- Kamchatka earthquakes (1737 and 1952).
- Lisbon earthquake (1755).
- New Madrid Earthquake (1811).
- Fort Tejon Earthquake (1857).
- Charleston earthquake (1886). Largest earthquake in the Southeast and killed 100.
- San Francisco Earthquake (1906).
- Great Kantō earthquake (1923). On the Japanese island of Honshu, killing over 140,000 in Tokyo and environs.
- Kamchatka earthquakes (1952 and 1737).
- Great Chilean Earthquake (1960). Biggest earthquake ever recorded, 9.5 on Moment magnitude scale.
- Good Friday Earthquake (1964) Alaskan earthquake.
- Ancash earthquake (1970). Caused a landslide that buried the town of Yungay, Peru; killed over 40,000 people.
- Sylmar earthquake (1971). Caused great and unexpected destruction of freeway bridges and flyways in the San Fernando Valley, leading to the first major seismic retrofits of these types of structures, but not at a sufficient pace to avoid the next California freeway collapse in 1989.
- Tangshan earthquake (1976). The most destructive earthquake of modern times. The official death toll was 255,000, but many experts believe that two or three times that number died.
- Great Mexican Earthquake (1985). 8.1 on the Ritcher Scale, killed over 6,500 people (though it is believed as many as 30,000 may have died, due to missing people never reappearing.)
- Whittier Narrows earthquake (1987).
- Armenian earthquake (1988). Killed over 25,000.
- Loma Prieta earthquake (1989). Severely affecting Santa Cruz, San Francisco and Oakland in California. Revealed necessity of accelerated seismic retrofit of road and bridge structures.
- Northridge, California earthquake (1994). Damage showed seismic resistance deficiencies in modern low-rise apartment construction.
- Great Hanshin earthquake (1995). Killed over 6,400 people in and around Kobe, Japan.
- İzmit earthquake (1999) Killed over 17,000 in northwestern Turkey.
- Düzce earthquake (1999)
- Chi-Chi earthquake (1999).
- Nisqually Earthquake (2001).
- Gujarat Earthquake (2001).
- Dudley Earthquake (2002).
- Bam Earthquake (2003).
- Parkfield, California earthquake (2004). Not large (6.0), but the most anticipated and intensely instrumented earthquake ever recorded and likely to offer insights into predicting future earthquakes elsewhere on similar slip-strike fault structures.
- Chuetsu Earthquake (2004).
- Indian Ocean Earthquake (2004). One of the largest earthquakes ever recorded at 9.0. Epicenter off the coast of the Indonesian island Sumatra. Triggered a tsunami which caused nearly 300,000 deaths spanning several countries.
- Sumatran Earthquake (2005).
- Fukuoka earthquake (2005).
- Kashmir earthquake (2005). Killed over 79,000 people. Many more at risk from the Kashmiri winter.
- Lake Tanganyika earthquake (2005). See also List of earthquakes

External links

- [http://www.eqnet.org/ EQNET: Earthquake Information Network]
- [http://neic.usgs.gov/ The U.S. National Earthquake Information Center]
- [http://earthquake.usgs.gov/faq/ USGS Earthquake FAQs]
- [http://www.ssn.unam.mx/ Mexican Sismological Service] Reports earthquakes in Mexico. Updated regularly.
- [http://wapi.isu.edu/envgeo/EG5_earthqks/eg_mod5.htm Environmental Geology - GEOL 406/506 (Earthquakes)]
- [http://www.quakes.bgs.ac.uk/hazard/ems1.htm The European Macroseismic Scale]
- [http://simscience.org/crackling/Advanced/Earthquakes/GutenbergRichter.html Gutenberg-Richter] power law of earthquake frequency against magnitude
- [http://www.guardian.co.uk/flash/0,5860,1121610,00.html Interactive guide: Earthquakes] an educational presentation on why earthquakes happen by Guardian Unlimited
- [http://www.geowall.org Geowall]- an educational 3d presentation system for looking at and understanding earthquake data
- [http://www.sciencecourseware.com/VirtualEarthquake/ Virtual Earthquake] educational site explaining how epicenters are located and magnitude is determined
- [http://www.pbs.org/newshour/science/earthquake/ PBS NewsHour - Predicting Earthquakes]
- [http://www.lamit.ro/earthquake-early-warning-system.htm Earthquake Warning System] Personal Earthquake warning system. Highly advanced detector, featuring sos signals and carrying strip.
- [http://www.data.scec.org/ Southern California Earthquake Data Center]
- [http://www.emsc-csem.org/ European-Mediterranean Seismological Centre (EMSC)]
- [http://www.gfz-potsdam.de/geofon/seismon/globmon.html Global Seismic Monitor at GFZ Potsdam]
- [http://earthquake.usgs.gov/bytopic/eqmonitoring/history/part09.php USGS Earthquake Monitoring History]
- [http://tsunami.geo.ed.ac.uk/local-bin/quakes/mapscript/demo_run.pl Global Earthquake Report – chart updated with each new earthquake or aftershock]
- [http://hraun.vedur.is/ja/englishweb/index.html Earthquakes in Iceland during the last 48 hours], updated automatically once every 2 minutes.
- [http://www.data.scec.org/recenteqs/Quakes/quakes0.html Recent earthquakes in California and Nevada ]
- [http://neic.usgs.gov/neis/eqlists/10maps_world.html USGS – Largest earthquakes in the world since 1900]
- [http://www.armageddononline.org/earthquake.php The Destruction of Earthquakes - and a List of the Worst ever recorded]
- [http://www.losangelesearthquakes.com Los Angeles Earthquakes plotted on a Google map]
- [http://rev.seis.sc.edu Seismograms for recent earthquakes via REV, the Rapid Earthquake Viewer]
- [http://www.iris.edu Incorporated Research Institutions for Seismology (IRIS)], earthquake database and software
- [http://www.iris.edu/seismon/ IRIS Seismic Monitor], world map of recent earthquakes
- [http://www.iris.edu/seismo/ SeismoArchives], Seismogram Archives of Significant Earthquakes of the World Category:Seismology Category:Geological hazards ko:지진 ms:Gempa bumi ja:地震 simple:Earthquake th:แผ่นดินไหว

Organism

In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. The origin of life and the relationships between its major lineages are controversial. Two main grades may be distinguished, the prokaryotes and eukaryotes. The prokaryotes are generally considered to represent two separate domains, called the Bacteria and Archaea, which are not closer to one another than to the eukaryotes. The gap between prokaryotes and eukaryotes is widely considered a major missing link in evolutionary history. Two eukaryotic organelles, namely mitochondria and chloroplasts, are generally considered to be derived from endosymbiotic bacteria. The phrase complex organism describes any organism with more than one cell.

Organizational terminology

Biological Organization

Viruses

Viruses are not typically considered to be organisms because they are not capable of independent reproduction or metabolism. However, according to the United States Code, they are considered to be microorganisms in the sense of biological weaponry and malicious use. This controversy is problematic, though, since some parasites and endosymbionts are incapable of independent life either. Although viruses do have enzymes and molecules characteristic of living organisms, they are incapable of surviving outside a host cell and most of their metabolic processes require a host and its 'genetic machinery'. The origin of such parasites is uncertain, but it appears most likely that they are derived from their host.

Life span

One of the basic parameters of organism is its life span. Some animals live as short as one day, while some plants can live thousands of years. Aging is important when determining life span of most organisms, bacterium, a virus or even a prion.

External links

- [http://news.bbc.co.uk/1/hi/sci/tech/944790.stm BBCNews: 27 September, 2000, When slime is not so thick] Citat: "...It means that some of the lowliest creatures in the plant and animal kingdoms, such as slime and amoeba, may not be as primitive as once thought...."
- [http://www.spaceref.com/news/viewpr.html?pid=4742 SpaceRef.com, July 29, 1997: Scientists Discover Methane Ice Worms On Gulf Of Mexico Sea Floor]
- [http://www.science.psu.edu/iceworms/iceworms.html The Eberly College of Science: Methane Ice Worms discovered on Gulf of Mexico Sea Floor] download Publication quality photos
- [http://www.sb-roscoff.fr/Ecophy/PDF/00-Fisher-NatWis.pdf Artikel, 2000: Methane Ice Worms: Hesiocaeca methanicola. Colonizing Fossil Fuel Reserves]
- [http://www.spaceref.com/news/viewnews.html?id=339 SpaceRef.com, May 04, 2001: Redefining "Life as We Know it"] Hesiocaeca methanicola In 1997, Charles Fisher, professor of biology at Penn State, discovered this remarkable creature living on mounds of methane ice under half a mile of ocean on the floor of the Gulf of Mexico.
- [http://news.bbc.co.uk/1/hi/sci/tech/2585235.stm BBCNews, 18 December, 2002, 'Space bugs' grown in lab] Citat: "...Bacillus simplex and Staphylococcus pasteuri...Engyodontium album...The strains cultured by Dr Wainwright seemed to be resistant to the effects of UV - one quality required for survival in space...."
- [http://news.bbc.co.uk/1/hi/sci/tech/3003946.stm BBCNews, 19 June, 2003, Ancient organism challenges cell evolution] Citat: "..."It appears that this organelle has been conserved in evolution from prokaryotes to eukaryotes, since it is present in both,"..."
- [http://www.anselm.edu/homepage/jpitocch/genbios/bi04syllabsu03.html Interactive Syllabus for General Biology - BI 04, Saint Anselm College, Summer 2003]
- [http://www.personal.psu.edu/users/j/s/jsf165/Bio110.html Jacob Feldman: Stramenopila]
- [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Root NCBI Taxonomy entry: root] (rich)
- [http://www.anselm.edu/homepage/jpitocch/genbios/surveybi04.html Saint Anselm College: Survey of representatives of the major Kingdoms] Citat: "...Number of kingdoms has not been resolved...Bacteria present a problem with their diversity...Protista present a problem with their diversity...",
- [http://www.species2000.org/ Species 2000 Indexing the world's known species]. Species 2000 has the objective of enumerating all known species of plants, animals, fungi and microbes on Earth as the baseline dataset for studies of global biodiversity. It will also provide a simple access point enabling users to link from here to other data systems for all groups of organisms, using direct species-links.
- [http://www.abc.net.au/science/news/enviro/EnviroRepublish_828525.htm The largest organism in the world may be a fungus carpeting nearly 10 square kilometers of an Oregon forest, and may be as old as 8500 years.]
- [http://tolweb.org/tree/phylogeny.html The Tree of Life]. zh-min-nan:Seng-bu̍t ko:생물 ja:生物 th:สิ่งมีชีวิต

Niche

There are several things called niche: #Generally, a niche is a special place within the scheme of things. It sometimes denotes the function or position of a thing within a structure. Niche is an English word of French origin. #Niche in architecture, see niche (architecture) #Niche in ecology, see ecological niche #Niche in industry, see niche (industry) ja:ニッチ

Landform

A landform comprises a geomorphological unit. Landforms are categorised by characteristics such as elevation, slope, orientation, stratification, rock exposure, and soil type. Landforms by name include berms, mounds, hills, cliffs, valleys, and so forth. Oceans and continents exemplify highest-order landforms. A number of factors, ranging from plate tectonics to erosion and deposition can generate and affect landforms. Biological factors can also influence landforms -- see for example the role of plants in the development of dune systems and salt marshes, and the work of corals and algae in the formation of coral reefs. coral reefs

List of landforms

- alas
- continent
- limestone pavement
- plain and plateau
- rock formations

Erosion landforms

Landforms produced by erosion and weathering usually occur in coastal or fluvial environments, and many appear above under those headings. Some other erosion landforms that do not fall into the above categories include:
- canyon
- cave
- limestone pavement
- tea table
- Deposition landform -- landforms produced by deposition of load or sediment (usually coastal or fluvial).
- Eolian landform - landforms produced by wind weathering.

External links

- [http://www.deh.gov.au/settlements/industry/minerals/booklets/landform/ Landform Design] Category:Geomorphology ja:地形

Beach

A beach or strand is a geological formation consisting of loose rock particles such as sand, shingle, cobble, or even shell along the shoreline of a body of water.

Components

Some geologists consider a beach to be just this shoreline feature of deposited material, but William Bascom (1980) has argued that a beach is the entire system of sand set in motion by waves to a depth of ten meters (30+ feet) or more off ocean coasts. Submerged, longshore bars are therefore also part of the beach. In the Bascom approach, beaches can be viewed as either
- small systems in which the rock material moves onshore, offshore, or alongshore by the forces of waves and currents; or
- geological units of considerable size. The former are described in detail below; the larger geological units are discussed elsewhere under bars. Both types can be viewed as "beaches." bars) is spreading from the incipient dune]] There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. That part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more longshore bars: slightly raised, underwater embankments formed where the waves first start to break. The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (that is, are sand), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune. The line between beach and dune is difficult to define in the field. Over any significant period of time, sand is always being exchanged between them. The drift line (the high point of material deposited by waves) is one potential demarcation. This would be the point at which significant wind movement of sand could occur, since the normal waves do not wet the sand beyond this area. However, the drift line is likely to move inland under assault by storm waves.

How beaches are formed

Beaches are deposition landforms, and are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles). Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. A coral reef offshore is a significant source of sand particles. coral reef The shape of a beach depends on whether the waves are constructive or destructive, and whether the material is sand or shingle. Constructive waves move material up the beach while destructive waves move the material down the beach. On sandy beaches, the backwash of the waves removes material forming a gently sloping beach. On shingle beaches the swash is dissipated because the large particle size allows percolation, so the backwash is not very powerful, and the beach remains steep. Cusps and horns form where incoming waves divide, depositing sand as horns and scouring out sand to form cusps. This forms the uneven edge of a sandy beach. coral reef Some beaches are artificial; they are either permanent or temporary (For examples see Monaco, Paris, Rotterdam, Hong Kong and Singapore). There are several beaches which are claimed to be the "World's longest", including Cox's Bazar, Bangladesh (120kms), Fraser Island beach, 90 Mile Beach in Australia and 90 Mile Beach in New Zealand and Long Beach, Washington (which is about 30km). Wasaga Beach, Ontario on Georgian Bay claims to have the world's longest freshwater beach. The Marina Beach at Chennai, India, is the second longest beach in the world.

Beaches and recreation

India] Beaches have long been a popular attraction for tourism and recreation. Especially popular are seaside resorts and large white sand beaches. Of course, residents and tourists alike use beaches as a place for leisure and sport. The relatively soft formation of sand is comfortable to sit or lie on, and entering and exiting the water is far easier across a sand beach than a rocky shore. The waves present at beaches add to the enjoyment and make the sport of body surfing and related activities possible. One of the many attractions of a sand beach, especially for children, is playing with the sand, building sand castles and other constructs. Towels and mats are typical beach "furniture". In the Victorian era, many popular beach resorts were equipped with bathing machines because even the all-covering beachware of the period was considered immodest. This social standard still prevails in some Muslim countries. At the other extreme are nude beaches, where no swimware of any kind is compulsory.

Artificial beaches

The soothing qualities of a beach and the pleasant environment offered to the beachgoer are replicated in artificial beaches, such as "beach style" pools with zero-depth entry and wave pools that recreate the natural waves pounding upon a beach. In a zero-depth entry pool, the bottom surface slopes gradually from above water down to depth. Another approach involves so-called urban beaches, a form of public park becoming common in large cities. Urban beaches attempt to mimic natural beaches with fountains that imitate surf and mask city noises, and in some cases can be used as a play park.

Sounds of the beach

park Beaches are noted for their sometimes serene stillness and the rhythmic sound made by waves crashing upon the sand. To experience, listen to this sound file sound recording (1.00MB) made on a South Carolina beach at night.

Beaches as habitat

A beach is an unstable environment which exposes plants and animals to harsh conditions. Some small animals burrow into the sand and feed on material deposited by the waves. Crabs, insects and shorebirds feed on these beach dwellers. The endangered Piping Plover and some tern species rely on beaches for nesting. Sea turtles also lay their eggs on ocean beaches. Seagrasses and other beach plants grow on undisturbed areas of the beach and dunes.

Reference

- Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.

External sites

- [http://www.unesco.org/csi/pub/source/ero9.htm UNESCO Beach erosion & formation]
- [http://www.nearctica.com/ecology/habitats/beaches.htm Beach habitats]
- Category:Landforms Category:Recreation ja:砂浜 simple:Beach

Category:Landforms

Category:Geography Category:Geomorphology ko:분류:지형 ja:Category:地形

Language Construction Kit

Language Construction Kit (auf deutsch etwa: Spachbaukasten) ist der Titel eines Dokuments im Format von HTML-Seiten von Autor Mark Rosenfelder. Gedacht ist es als Anleitung zum Erstellen von konstruierten Sprachen. Sein Aufbau ist systematisch, von den einfachsten Bausteinen einer Sprache bis zu den komplexesten. Beginnend mit der Phonologie und dem Schriftsystem gehts es über die Wortbildung und Worte zu dem aufwendigen Gebiet der Grammatik und endet bei beim Überblick über Register und Dialekte. Der rezeptartige Aufbau, zusammen mit Warnungen vor Dingen, die man gewöhnlich leicht übersehen kann, gepaart mit einer Vielzahl von Beispielen aus natürlichen Sprachen und einer guten Prise Humor haben dazu geführt, dass diese Spachbauanleitung unter den Mitgliedern der Internet-Community der Sprachbau-Begeisterten (conlang-Community) einen gewissen Status von Respekt und Bekanntheit erreicht hat. Das Original ist in Englisch, Liebhaber haben eine portugiesische und eine italienische Übersetzung bereitgestellt.

Siehe auch

- Portal:Konstruierte Sprachen
- Konstruierte Sprache
- Plansprache

Weblinks

- [http://www.zompist.com/kit.html Language Construction Kit] (englisch)
- [http://www.zompist.com/langfaq.html langfaq] - die FAQ-Sammlung der Newsgroup sci.lang (englisch)

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Wave cut platform

Wave

The medium which carries a wave

Examples of waves

Characteristic properties

Transverse and longitudinal waves

Polarization

Physical description of a wave

Travelling waves

Propagation through strings

The wave equation

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See also

Earthquake

Characteristics

Earthquake Size

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Specific fault articles

Specific earthquake articles

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Organism

Organizational terminology

Viruses

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Niche

Landform

See also

List of landforms

Slope landforms

Coastal and oceanic landforms

Fluvial landforms

Mountain and glacial landforms

Volcanic landforms

Erosion landforms

External links

Beach

Components

How beaches are formed

Beaches and recreation

Artificial beaches

Sounds of the beach

Beaches as habitat

See also

Reference

External sites

Category:Landforms

Language Construction Kit

Siehe auch

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